1. Field of the Invention
The present invention relates to a camera device and a related focusing method, and more particularly, to a camera device and a related auto-focusing method capable of actively varying a focal length of a lens of the camera device according to time variation.
2. Description of the Prior Art
A conventional camera device usually has a day mode and a night mode. In the day mode, an infrared optical filter is added on the image sensor of the camera device to prevent the monitor image from color shift affected by infrared ray; and in the night mode, the camera device can receive the infrared ray via removal of the infrared optical filter to increase photosensitivity of the image sensor on the camera device.
Imaging position of the image sensor is effected by refraction of the infrared optical filter, the image sensor can capture the clear monitoring image through the infrared optical filter in the day mode, and the monitoring image is easily defocused in the night mode without usage of the infrared optical filter. The conventional solution is adapted to drive an focusing process of the camera device for acquiring the clear monitoring image; however, the conventional focusing process spends more executive time, the camera device cannot capture the monitoring image while executing the focusing process, which results in a drawback of uncompleted monitoring observation. Thus, design of a monitoring method capable of solving the drawback of uncompleted monitoring observation resulted from the defocused switched between the day mode and the night mode is an important issue in the related industry.